High disease levels and variable winter crops yields captured in RL harvest results

Many Recommended Lists (RL) harvest results are now available for major winter crops, with some very high disease levels and variable yields recorded. Jason Pole provides an at-a-glance summary of the latest picture from the variety trials for cereals and oilseeds.

The UK’s winter combinable crops weathered prolonged wet and mild spells throughout most of the growing season. In recent weeks, commercial harvest has progressed at pace, with below-average yields recorded for many winter crops. Crop and weather conditions have also caused some delays in combining, especially in winter wheat.  

The season’s impact on varieties in RL is becoming clearer as more harvest results are released. Although harvest 2024 yield averages are close to over-year averages, the challenging growing season led to some very high disease levels and variable yields across the variety-trial network. Additionally, several trials have been abandoned due to poor crop condition.

In the RL winter crop trials, winter barley appears to have fared the best. Overall, fungicide-treated yields are slightly above the five-year average control yield. Trials were established in good conditions, well before the weather broke. Apart from some localised waterlogging, trials wintered well.

The most notable diseases were brown rust and rhynchosporium, which were common in fungicide-untreated trials. In the runup to harvest, strong wind and rain at some sites caused lodging and brackling in the weaker-strawed varieties. Over half of the results for this crop are now available.

Winter oats also went in before the most challenging autumn weather and established well (overall, fungicide-treated yields are about average).

Very high levels of crown rust were seen in some fungicide-untreated trials in southern England. Sometimes, infection was so severe that varieties failed to properly head. Lodging was also widespread, even in PGR-treated crops. Most results are now available for this crop.

It has been a very difficult season for commercial and RL oilseed rape crops. This year, we had to abandon almost half (9/19) of the fungicide-treated trials and nearly all (6/7) of the fungicide-untreated trials. The impact of relentless wet weather, flea beetle feeding and pigeon grazing all added up. In some trials, clubroot and light leaf spot were problematic too. The latter caused some severe plant stunting (something we rarely see).

Results from the surviving 10 fungicide-treated trials are available. The average yield of the control varieties is 4.92 t/ha (the four-year average is 5.05 t/ha).

The performance of winter oilseed rape is often more variable than cereals (both within and between trials). Variability is particularly stark this year. The lowest-yielding trial (Midlothian) and two highest-yielding trials (both in Cambridgeshire) saw the controls yield 3.58 t/ha and 6.08 t/ha, respectively.

On Friday we published the first RL harvest results for winter wheat, adding more sites today (27 August 2024). It takes the total fungicide-treated sites reported on to nine.

As in commercial crops, when crops were drilled after the weather broke in mid-October, they struggled. In fact, several trials were lost because of waterlogging and flooding, particularly through the middle of England.

Disease was quick to get going in the spring. Although considered a late-season disease, we reported on very early brown rust infection in RL trials and commercial crops at the start of May.

The RL is dominated by varieties with moderate levels of resistance (disease ratings 5, 6 and 7) and we recorded some of the highest brown rust levels for many years in untreated trials. We also saw high levels of septoria tritici.

Until recently, we aimed to keep disease below 5% in fungicide-treated trials. If disease was above this, the yield information would not have been used in the main data set. However, with the chemistry now available, we can no longer hope to keep disease below 5%, especially in a high-disease-pressure year, such as 2024.

With the potential to lose large amounts of data, we now include data from fungicide-treated yield trials even when disease exceeds 10% (if the fungicide protocol has been followed). The revised RL protocols now better assess genetic potential in context with the fungicides available to us today.

The treated control yield average for the first sites is slightly below the five-year average of 10.95 t/ha, pulled down by some low-yielding trials in the latest data release.

With more than 20 trials due to report, it is early days for this data set.

Our harvest results service delivers the latest data and commentary from the RL trials. Visit the web page for the latest information and to sign up for the harvest results emails.